[en] Secondary uranium mineral-bearing calcrete formations have been located for the first time in India at Kanji Ki Sird (27°29 min 30 secN, 72°28min 06 secE) and Jodhsingh Ki Sird (27°29 min17 sec N, 72°29 min 04 secE) areas in Thar Desert environs of the Jodhpur district of Rajasthan. Seven zones of uraniferous calcretes in varying dimensions from 25 m x 25 m to 500 m x 200 m have been delineated by pitting and trenching over an area of 2 sq. km. The thickness of the uraniferous (assayed up to 0.047% U_3O_8 and chemical up to 0.024% U_3O_8) calcrete horizon varies from 30 cm to about a meter. These zones fall within a half-kilometer wide WNW-ESE trending low gradient drainage channel. Greenish to yellowish coloured secondary uranium minerals occur along cavities, vugs and fractures in calcretes and along rock fragment boundaries. Uranium minerals identified by X-ray diffraction technique are tyuyamunite (Ca(UO_2)_2(VO_4)_2_._5-8H_2_O), wyartite (Ca_3U (UO_2)_6(CO_3)_2(OH)_1_63-5 H_2O) and meta-autunite (Ca(UO_2)_2(PO_4)_2_.10-12H_2O). The Bap Boulder Bed and Badhaura sandstone exposed in the catchment area are the provenance rocks for uranium. (author)

[en] India is deficient in both gold and uranium resources. Almost one-third of the annual global mine production of ∼2500 tonnes of gold is imported into India to fulfil the high gold consumption. Uranium is important for production of nuclear energy, more specifically to execute the country's ambitious programme to generate 20 GW of electricity by 2020

[en] Uranium mineralization associated with sulphide bearing sheared/brecciated quartzite in North Delhi Fold Belt is known from Raghunathgarh area of Sikar district, Rajasthan. Here, the surface mineralisation occurs intermittently over 1.5 km with samples (n=21) analysing 0.014-0.710% U₃O₈ (Av. 0.162%) with negligible thorium. Uraninite, along with other secondary minerals, occurs as fine sized grains along fracture planes, around grain boundaries and also as fine sized grains forming small clusters. The sulfides include pyrite, pyrhotite, and chalcopyrite. Magnetite is also present. Considering the promising surface indications, structural control and association of uranium mineralisation with sulfides, magnetic, IP/resistivity and EM surveys were carried out to delineate subsurface structural features and conductors in the area. A sizeable part of the area is covered with sand dunes and soil. The magnetic survey revealed two sub-surface faults, one of which is parallel to a shear and the mineralized zone. EM conductor axis, as marked by the EM survey, extends over a strike length of about 800m and again for 400m with a lateral shift. A prominent NE-SW trending high chargeability and corresponding low resistivity zone and a magnetic low depicting a fracture zone was identified in the NW part of the explored area. Based on the geological and geophysical data and the surface indications, sub-surface exploration was taken up at Raghunathgarh and a total of 42 boreholes have been completed so far. It is observed that the EM conductor axis and one of the faults delineated from the magnetic survey broadly coincide with the mineralization bands intercepted in some of the boreholes. A few boreholes were also drilled to test the NE-SW trending high chargeability/low resistivity zone corresponding to carbonaceous phyllite, clay, disseminated sulphides and the fracture zone marked by a magnetic low in the NW part. Core examination indicated the presence of varied lithounits, mainly quartzite, quartz-biotite/chlorite schist, biotite schist, amphibolite, carbonaceous phyllite and quartz veins. The sub-surface exploration has, so far outlined four correlatable mineralized lodes with strike lengths of 400 m, 300 m, 200 m and 160 m respectively within a explored length of about 2.5 km. (author)

[en] Uranium - thorium mineralization in Belwa, Devtalai and Gudalia areas is hosted in pink phase of Berach Granite (BG) at the western intrusive contact with the rocks of Mangalwar Complex (MC) in the northern apical region of the granite body. It occurs at the foot wall side of copper mineralization that is associated with quartz reefs. Although surface manifestation of mineralization is limited, its subsurface continuity has been traced over 5 km length in between Belwa and Gudalia. Core samples of pink granite have radiometrically assed from 0.014 to 0.036% U_3O_8, <0.01 to 0.032% U_3O_8 and <0.005 to 0.015 ThO_2. The Berach Granite (BG) has two phases. An early grey and later pink phase. The pink variety hosts mineralization and is a high silica, low-Ca and peraluminous granite, while the grey granite is characterised by low-silica and high-Ca content. Mineralisation falls along the Bharatpur-Mount Abu lineament, close to thrust zone of Mangalwars and Jahazpurs. Radioactivity due to uranium and thorium in pink granite is associated with titanomagnetite, zircon, ilmenite and monazite. (author)

[en] A number of albitite occurrences have been reported amidst Archaean basement and the Meso-Proterozoic cover rocks of Delhi Supergroup in north-central and northern Rajasthan. These occurrences form a linear zone about 130 km in length and 5-12 km in width from Neorana in the north to Nayagaon in the south. This zone has a regional NE-SW trend and occurs about 20-40 km east of known albitite line. We report here a zone of albitite and albitized rocks in the Banded Gneissic Complex (BGC) around Bichun, Nayagaon, Asalpur and Dungarwara and amidst Delhi Supergroup rocks in the East Khetri basin around Chiplata, Sirsori ki Dhani, Ghasipura, Rela and Neorana. The delineated albitite occurrences are radioactive and some of them host significant uranium and REE, Y and Sc. These albitite occurrences represent a intracontinental rift zone parallel to the one established by Ray and assume significance for exploration for uranium and other polymetallic minerals (REE, Y and Sc)

[en] A narrow linear belt (60 km x 3-12 km) of Palaeo to Meso-Proterozoic supracrustals occurring between Archaean Singhbhum granitoid (SG) and Koira synclinorium of Iron Ore Group (IOG) in the western margin of Singhbhum Orissa Craton is known as Kolhan Basin. The sandstone-carbonate-shale intracratonic litho-package deposited unconformably over Singhbhum granite and Iron Ore Group are mostly undeformed and unmetamorphosed. Kolhan equivalent rocks are exposed in Chamakpur-Keonjhar Basin, Mankarchuan basin in the western part and Sarapalli-Kamakshyanagar quartzite band in the southwestern part of the Singhbhum Orissa Craton (SOC). Limited geological and radiometric studies conducted by Atomic Minerals Directorate for Exploration and Research (AMD) indicated presence of uranium, predominant thorium and mixed (U+Th) anomalies associated with the basal conglomerate-sandstone sequence at several places. In Kokrajhar nala section radioactive conglomeratic sandstone boulders are found to contain uraninite and metatorbernite. Th and mix U+Th anomaly zones contain monazite, xenotime, zircon, sphene and rutile as significant accessory minerals. Favourable Palaeo and Meso-Proterozoic time hiatus, fertile basement rocks, presence of palaeosols and undeformed red bed fluviatile clastics overlain by marine evaporite, large ductile shear zones in basement, reverse fault structures transecting the unconformity and the basinal sediments, suspected alteration features viz, illitisation and kaolinisation near unconformity, reductants in the form of carbonaceous shale, basic dykes and Fe-Mg alteration zones along with the occurrence of several radioactive anomalies are the factors invoked to construe unconformity-related uranium mineralization in Kolhan basin. Probabilities and prospects are discussed in the light of recently developed concepts and alternative exploration methodology and strategy have been suggested to build up an exploration model. (author)

[en] Significant sandstone-type uranium mineralisation is recorded from the Rongcheng Plateau and Rongdinala, located north and WNW of Balphakram Plateau, South Garo Hills district, Meghalaya. Mineralisation is associated with grey coloured, medium to coarse grained, poorly sorted arkosic Wacke-Subarkose suite of sandstones, belonging to the late Cretaceous Mahaek Formation. Sixteen uranium occurrences located 2-30 m above crystalline basement and with dimensions varying from 5 to 300 m x 0.5 to 4 m, have been identified. Grab samples have assayed up to 0.52% eU₃O₈, 0.46% U₃O₈ (beta/gamma) and <0.010% ThO₂. The fertile precambrian basement crystallines constitute the source of uranium. Presence of organic matter and pyrite in the sandstone provided reducing environment for deposition of pitchblende as the principal discrete uranium mineral. (author)

[en] Uranium mineralization in Bichun area, Jaipur district, Rajasthan, India is hosted by albitites within the Banded Gneissic Complex (BGC). Detailed mineralogical and EPMA studies reveal the presence of davidite along with brannerite and uraninite. The U - Pb concordia upper intercept age of 933 ± 13 Ma and Pb - Pb isochron age of 930 ± 4 Ma, on pure davidite fractions indicate the timing of uranium mineralizing event to be ca. 930 Ma. The timing of uranium mineralization can be correlated with the Grenvillian orogeny (ca. 1000 Ma). The Sm - Nd model age (T_D_M) of davidite is varies from 1851 to 2200 Ma with ε_N_d_i_(_9_3_0 _M_a_) ranging from -10.7 to -15.5 which shows that the Palaeoproterozoic rocks with crustal component (either within BGC or basement granite) are the source for uranium. (author)